Solar panels are tested at a standard temperature of 25°C (77°F), but Arizona summer days routinely push panel surface temperatures to 65–75°C (150–167°F). Heat reduces panel output — a phenomenon measured by a panel's temperature coefficient. Despite this, Arizona's outstanding solar resource still produces excellent annual output. Understanding heat losses helps you choose the right panels and manage expectations accurately.
For guidance on which panel brands perform best in Arizona's heat, see our best solar panels for Arizona heat guide. For full system cost context, see our Arizona solar cost guide. For the full picture on going solar, see our step-by-step going solar guide.
What Is Temperature Coefficient?
Every solar panel has a temperature coefficient of power (Pmax) listed in its specifications. This number tells you how much panel output decreases for every degree Celsius above 25°C (the test standard temperature). It's expressed as a percentage per degree.
Example Calculation
A panel with a temperature coefficient of −0.35%/°C on a 115°F (46°C) day:
- Air temperature: 46°C
- Panel surface temperature: approximately 46°C + 25°C = ~71°C (panels run significantly hotter than air)
- Temperature above standard (25°C): 71°C − 25°C = 46°C above standard
- Power loss: 46°C × 0.35%/°C = 16.1% reduction in output
- A 400W panel produces approximately 335W instead of 400W in these conditions
Temperature Coefficient by Panel Type
| Panel Technology | Typical Temp Coefficient | Loss at 71°C Panel Temp | AZ Performance Rating |
|---|---|---|---|
| Standard monocrystalline PERC | −0.34 to −0.40%/°C | 16–21% | Average |
| TOPCon (n-type) | −0.28 to −0.35%/°C | 13–16% | Good |
| HJT (heterojunction) | −0.24 to −0.28%/°C | 11–13% | Excellent |
| Back-contact (SunPower IBC) | −0.27%/°C | ~12% | Excellent |
| Standard polycrystalline | −0.40 to −0.45%/°C | 19–23% | Below average |
Annual Production: Still Excellent Despite Summer Heat
Heat reduces output in summer, but Arizona's winter and spring solar production is exceptional — mild temperatures, clear skies, and strong irradiance from February through May. The annual picture:
- Arizona annual production estimate: ~1,650 kWh/kW of installed capacity (vs. ~1,200 kWh/kW in cloudy Northern states)
- Summer months: High irradiance but heat losses reduce efficiency
- Winter months: Lower sun angle but excellent panel efficiency at cooler temperatures
- Net result: Arizona panels produce significantly more annually than in most U.S. states, even accounting for heat losses
Production estimates built into solar quotes should already account for temperature derating — ask your installer if their estimate uses a location-specific performance ratio that includes temperature derating for Arizona's climate.
See Your Arizona Production Estimate
Our calculator uses Arizona-specific production factors including temperature derating for an accurate estimate.
Calculate My Production →How Roof and Mounting Affect Heat Losses
Airflow Under Panels
Panels mounted close to the roof (1–2 inches clearance) trap heat and run hotter than panels with better airflow underneath. Most residential installations use standard racking that provides some airflow, but the gap matters:
- Tile roofs naturally provide more airflow under panels than flat roof-penetrating racking systems
- Some racking systems offer elevated configurations for better cooling — worth asking about in Arizona
- Flat roof ballasted systems can be tilted and positioned to maximize airflow
Roof Color and Material
- Dark roof materials (asphalt shingles) absorb more heat, raising panel temperatures
- Light-colored or reflective roofs (white TPO, light tile) keep panels cooler
- A light-colored roof can reduce panel temperatures by 5–10°C, recovering 2–4% of heat losses
Attic Ventilation
Well-ventilated attics keep roof deck temperatures lower, indirectly reducing panel operating temperatures. If your attic runs extremely hot (common in Arizona), improving ventilation can have multiple benefits including better solar performance.
Do Heat Losses Affect Panel Warranties?
No — panel warranties guarantee output over time (typically 80% or more at 25 years) regardless of climate. Heat-related output variation is expected operating behavior, not a warranty defect. Arizona panels produce somewhat less per-watt in summer than cooler climates but their warranty terms are identical. The annual production differential is already accounted for in Arizona-specific production estimates.
Tips for Maximizing Output in Arizona's Heat
- Choose low-temperature-coefficient panels: HJT and IBC panels (REC Alpha, Panasonic EverVolt, SunPower Maxeon) have the best heat tolerance
- Ensure adequate racking clearance: Ask your installer about airflow under panels
- Consider a light-colored roof: If you're reroofing, cool-roof materials improve panel performance
- Accept the seasonal pattern: Arizona solar produces heavily in spring (excellent conditions) and moderately in summer despite heat losses — annual production is still excellent
- Review your production estimate: Confirm your installer's production estimate includes Arizona-specific climate adjustments
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